Multi-speed transmission

ABSTRACT

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices include clutches and a brake.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/953,085 filed on Jul. 31, 2007. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches, planetary gear arrangements and fixed interconnections toachieve a plurality of gear ratios. The number and physical arrangementof the planetary gear sets, generally, are dictated by packaging, costand desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member,four planetary gear sets, a plurality of coupling members and aplurality of torque transmitting devices. Each of the planetary gearsets includes first, second and third members. The torque transmittingdevices are for example clutches and a brake.

An embodiment of the transmission of the present Invention includes aninput member, an output member, first, second, third and fourthplanetary gear sets each having first, second and third members. A firstinterconnecting member continuously interconnecting the second member ofthe first planetary gear set with a stationary element, a secondinterconnecting member continuously interconnecting the third member ofthe first planetary gear set with the first member of the secondplanetary gear set, a third interconnecting member continuouslyinterconnecting the third member of the second planetary gear set withthe first member of the third planetary gear set, and a fourthinterconnecting member continuously interconnecting the third member ofthe third planetary gear set and the third member of the fourthplanetary gear set. Five torque transmitting mechanisms are selectivelyengageable to interconnect one of the first, second, and third memberswith at least one of the first members, second members, third members,and the stationary element. The torque transmitting mechanisms areselectively engageable in combinations of at least two to establish atleast eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.

In one aspect of the present invention, a first of the five torquetransmitting mechanisms is selectively engageable to interconnect atleast one of the first member of the first planetary gear set, thesecond member of the second planetary gear set, and the input memberwith the first member of the fourth planetary gear set.

In another aspect of the present invention, a second of the five torquetransmitting mechanisms is selectively engageable to interconnect atleast one of the third member of the first planetary gear set and thefirst member of the second planetary gear set with the first member ofthe fourth planetary gear set.

In yet another aspect of the present invention, a third of the fivetorque transmitting mechanisms is selectively engageable to interconnectat least one of the second member of the third planetary gear set andthe output member with the first member of the fourth planetary gearset.

In yet another aspect of the present invention, a fourth of the fivetorque transmitting mechanisms is selectively engageable to interconnectthe second member of the fourth planetary gear set with the first memberof the fourth planetary gear set.

In yet another aspect of the present invention, a fifth of the fivetorque transmitting mechanisms is selectively engageable to interconnectthe second member of the fourth planetary gear set with the stationaryelement.

In yet another aspect of the present invention, the first members aresun gears, the second members are carrier members, and the third membersare ring gears.

In yet another aspect of the present invention, the input member iscontinuously interconnected with the first member of the first planetarygear set and the second member of the second planetary gear set andwherein the output member is continuously interconnected with the secondmember of the third planetary gear set.

In yet another aspect of the present invention, one of the torquetransmitting mechanisms is a brake and four of the torque transmittingmechanisms are clutches.

In yet another aspect of the present invention, the stationary elementis a transmission housing.

Another embodiment of the transmission of the present invention includesan input member, an output member, first, second, third and fourthplanetary gear sets each having first, second and third members, whereinthe input member is continuously interconnected with the first member ofthe first planetary gear set and the second member of the secondplanetary gear set and wherein the output member is continuouslyinterconnected with the second member of the third planetary gear set. Afirst interconnecting member continuously interconnecting the secondmember of the first planetary gear set with a stationary element, asecond interconnecting member continuously interconnecting the thirdmember of the first planetary gear set with the first member of thesecond planetary gear set, a third interconnecting member continuouslyinterconnecting the third member of the second planetary gear set withthe first member of the third planetary gear set, and a fourthinterconnecting member continuously interconnecting the third member ofthe third planetary gear set and the third member of the fourthplanetary gear set. A first torque transmitting mechanism is selectivelyengageable to interconnect at least one of the first member of the firstplanetary gear set, the second member of the second planetary gear set,and the input member with the first member of the fourth planetary gearset. A second torque transmitting mechanism is selectively engageable tointerconnect at least one of the third member of the first planetarygear set and the first member of the second planetary gear set with thefirst member of the fourth planetary gear set. A third torquetransmitting mechanism is selectively engageable to interconnect atleast one of the second member of the third planetary gear set and theoutput member with the first member of the fourth planetary gear set. Afourth torque transmitting mechanism is selectively engageable tointerconnect the second member of the fourth planetary gear set with thefirst member of the fourth planetary gear set. A fifth torquetransmitting mechanism is selectively engageable to interconnect thesecond member of the fourth planetary gear set with the stationaryelement. The torque transmitting mechanisms are selectively engageablein combinations of at least two to establish at least eight forwardspeed ratios and at least one reverse speed ratio between the inputmember and the output member.

In one aspect of the present invention, the first members are sun gears,the second members are carrier members, and the third members are ringgears.

In another aspect of the present invention, the stationary element is atransmission housing.

Another embodiment of the transmission of the present invention includesan input member, an output member, first, second, third and fourthplanetary gear sets each having a sun gear, a carrier member, and a ringgear, wherein the input member is continuously interconnected with thesun gear of the first planetary gear set and the carrier member of thesecond planetary gear set and wherein the output member is continuouslyinterconnected with the carrier member of the third planetary gear set.A first interconnecting member continuously interconnecting the carriermember of the first planetary gear set with a stationary element, asecond interconnecting member continuously interconnecting the ring gearof the first planetary gear set with the sun gear of the secondplanetary gear set, a third interconnecting member continuouslyinterconnecting the ring gear of the second planetary gear set with thesun gear of the third planetary gear set, a fourth interconnectingmember continuously interconnecting the ring gear of the third planetarygear set and the ring gear of the fourth planetary gear set. A firsttorque transmitting mechanism is selectively engageable to interconnectat least one of the sun gear of the first planetary gear set, thecarrier member of the second planetary gear set, and the input memberwith the sun gear of the fourth planetary gear set. A second torquetransmitting mechanism is selectively engageable to interconnect atleast one of the ring gear of the first planetary gear set and the sungear of the second planetary gear set with the sun gear of the fourthplanetary gear set. A third torque transmitting mechanism is selectivelyengageable to interconnect at least one of the carrier member of thethird planetary gear set and the output member with the sun gear of thefourth planetary gear set. A fourth torque transmitting mechanism isselectively engageable to interconnect the carrier member of the fourthplanetary gear set with the sun gear of the fourth planetary gear set. Afifth torque transmitting mechanism is selectively engageable tointerconnect the carrier member of the fourth planetary gear set withthe stationary element. The torque transmitting mechanisms areselectively engageable in combinations of at least two to establish atleast eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.

In one aspect of the present invention, the stationary element is atransmission housing.

Further objects, aspects and advantages of the present invention willbecome apparent by reference to the following description and appendeddrawings wherein like reference numbers refer to the same component,element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of an eight speedtransmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of an eight speedtransmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting elements in each of the available forwardand reverse speeds or gear ratios of the transmission illustrated inFIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that the embodiments of theeight speed automatic transmission of the present invention have anarrangement of permanent mechanical connections between the elements ofthe four planetary gear sets. A first component or element of the firstplanetary gear set is permanently coupled to ground, stationary element,or a transmission housing. A second component or element of a firstplanetary gear set is permanently coupled to a second component orelement of a second planetary gear set. A third component or element ofthe first planetary gear set is permanently coupled to a third componentor element of the second planetary gear set. A first component orelement of the second planetary gear set is permanently coupled to firstcomponent or element of a third planetary gear set. A second componentor element of the third planetary gear set is permanently coupled to asecond component or element of a fourth planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear set are each represented by a node. Therefore, a single levercontains three nodes: one for the sun gear, one for the planet gearcarrier, and one for the ring gear. The relative length between thenodes of each lever can be used to represent the ring-to-sun ratio ofeach respective gear set. These lever ratios, in turn, are used to varythe gear ratios of the transmission in order to achieve appropriateratios and ratio progression. Mechanical couplings or interconnectionsbetween the nodes of the various planetary gear sets are illustrated bythin, horizontal lines and torque transmitting devices such as clutchesand brakes are presented as interleaved fingers. If the device is abrake, one set of the fingers is grounded. Further explanation of theformat, purpose and use of lever diagrams can be found in SAE Paper810102, “The Lever Analogy: A New Tool in Transmission Analysis” byBenford and Leising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The input member 12 is coupled to the third node 14C of the firstplanetary gear set 14. The output member 22 is coupled to the secondnode 18B of the third planetary gear set 18. The first node 14A of thefirst planetary gear set 14 is coupled to the first node 16A of thesecond planetary gear set 16. The second node 14B of the first planetarygear set 14 is permanently connected to a ground, stationary element, ortransmission housing 50. The third node 14C of the first planetary gearset 14 is permanently connected to the second node 16B of the secondplanetary gear set 16. The third node 16C of the second planetary gearset 16 is permanently connected to the third node 18C of the thirdplanetary gear set 18. The first node 18A of the third planetary gearset 18 is permanently connected to the second node 20B of the fourthplanetary gear set 20.

A first clutch 26 selectively connects the second node 16B of the secondplanetary gear set 16 to the third node 20C of the fourth planetary gearset 20. A second clutch 28 selectively connects the first node 16A ofthe second planetary gear set 16 to the third node 20C of the fourthplanetary gear set 20. A third clutch 30 selectively connects the thirdnode 20C of the fourth planetary gear set 20 to output member 22 and tothe second node 18B of the third planetary gear set 18. A fourth clutch32 selectively connects the first node 20A of the fourth planetary gearset 20 to the third node 20C of the fourth planetary gear set 20. Abrake 34 selectively connects the first node 20A of the fourth planetarygear set 20 to the ground, stationary element, or transmission housing50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brake and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, the planetary gear set 14 includes a sun gear member 14C, aplanet gear carrier member 14B and a ring gear member 14A. The sun gearmember 14C is connected for common rotation to input member 12. The ringgear member 14A is connected for common rotation to a first shaft orinterconnecting member 44. The planet gear carrier member 14B rotatablysupports a set of planet gears 14D (only one shown) and is connected totransmission housing 50 through a second shaft or interconnecting member46. The planet gears 14D are each configured to intermesh with the bothsun gear member 14C and the ring gear member 14A.

The input shaft or member 12 is preferably continuously connected to anengine (not shown) or to a turbine of a torque converter (not shown).The output shaft or member 22 is preferably continuously connected withthe final drive unit or transfer case (not shown).

The planetary gear set 16 includes a sun gear member 16A, a ring gearmember 16C and a planet carrier member 16B that rotatably supports a setof planet gears 16D. The sun gear member 16A is connected for commonrotation with the first shaft or interconnecting member 44. The ringgear member 16C is connected for common rotation with a third shaft orinterconnecting member 48. The planet carrier member 16B is connectedfor common rotation with the input shaft or member 12 and a fourth shaftor interconnecting member 52. The planet gears 16D are each configuredto intermesh with both sun gear member 16A and ring gear member 16C.

The planetary gear set 18 includes a sun gear member 18C, a ring gearmember 18A and a planet carrier member 18B that rotatably supports a setof planet gears 18D. The sun gear member 18C is connected for commonrotation with the third shaft or interconnecting member 48. The ringgear member 18A is connected for common rotation with a fifth shaft orinterconnecting member 54. The planet carrier member 18B is connectedfor common rotation with the output shaft or member 22 and with a sixthshaft or interconnecting member 56. The planet gears 18D are eachconfigured to intermesh with both the sun gear member 18C and the ringgear member 18A.

The planetary gear set 20 includes a sun gear member 20C, a planetcarrier member 20A that rotatably supports a first set of planet gears20D and a second set of planet gears 20E, and a ring gear member 20B.The sun gear member 20C is connected for common rotation with a seventhshaft or interconnecting member 58. The planet carrier member 20A isconnected for common rotation with an eighth shaft or interconnectingmember 60 and a ninth shaft or interconnecting member 62. The ring gearmember 20B is connected for common rotation with the fifth shaft orinterconnecting member 54. The first set of planet gears 20D are eachconfigured to intermesh with both the ring gear member 20B and thesecond set of planet gears 20E. The second set of planet gears 20E areeach configured to intermesh with both the sun gear member 20C and thefirst set of planet gears 20D.

The torque-transmitting mechanisms or clutches 26, 28, 30 and 32 andbrake 34 allow for selective interconnection of the shafts orinterconnecting members, members of the planetary gear sets and thehousing. For example, the first clutch 26 is selectively engageable toconnect the fourth shaft or interconnecting member 52 to the seventhshaft or interconnecting member 58. The second clutch 28 is selectivelyengageable to connect the first shaft or interconnecting member 44 tothe seventh shaft or interconnecting member 58. The third clutch 30 isselectively engageable to connect the sixth shaft or interconnectingmember 56 to the seventh shaft or interconnecting member 58. The fourthclutch 32 is selectively engageable to connect the seventh shaft orinterconnecting member 58 to the ninth shaft or interconnecting member62. The brake 34 is selectively engageable to connect the eighth shaftor interconnecting member 60 to ground, stationary element, ortransmission housing 50 in order to restrict planet carrier member 20Afrom rotating relative to the ground, stationary element, ortransmission housing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat transmission 10 is capable of transmitting torque from the inputshaft or member 12 to the output shaft or member 22 in at least eightforward speed or torque ratios and at least one reverse speed or torqueratio with a double overdrive. Each forward and reverse speed or torqueratio is attained by engagement of one or more of thetorque-transmitting mechanisms (i.e. first clutch 26, second clutch 28,third clutch 30, fourth clutch 32, and brake 34), as will be explainedbelow. FIG. 3 is a truth table presenting the various combinations oftorque-transmitting mechanisms that are activated or engaged to achievethe various gear states. Actual numerical gear ratios of the variousgear states are also presented although it should be appreciated thatthese numerical values are exemplary only and that they may be adjustedover significant ranges to accommodate various applications andoperational criteria of the transmission 10. An example of the gearratios that may be obtained using the embodiments of the presentinvention are also shown in FIG. 3. Of course, other gear ratios areachievable depending on the gear diameter, gear teeth count and gearconfiguration selected.

To establish reverse gear, the second clutch 28 and the third clutch 30are engaged or activated. The second clutch 28 connects the first shaftor interconnecting member 44 to the seventh shaft or interconnectingmember 58. The third clutch 30 connects the sixth shaft orinterconnecting member 56 to the seventh shaft or interconnecting member58. Likewise, the eight forward ratios are achieved through differentcombinations of clutch and brake engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and the brake not specifically referenced in agiven gear state are inactive or disengaged and, second of all, thatduring gear shifts, i.e., changes of gear state, between at leastadjacent gear states, a clutch or brake engaged or activated in bothgear states will remain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a first interconnecting member continuouslyinterconnecting the second member of the first planetary gear set with astationary element; a second interconnecting member continuouslyinterconnecting the third member of the first planetary gear set withthe first member of the second planetary gear set; a thirdinterconnecting member continuously interconnecting the third member ofthe second planetary gear set with the first member of the thirdplanetary gear set; a fourth interconnecting member continuouslyinterconnecting the third member of the third planetary gear set and thethird member of the fourth planetary gear set; and five torquetransmitting mechanisms each selectively engageable to interconnect oneof the first, second, and third members with another one of the firstmembers, second members, third members, and the stationary element, andwherein the torque transmitting mechanisms are selectively engageable incombinations of at least two to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member and wherein one of the torque transmitting mechanismsis a brake and four of the torque transmitting mechanisms are clutches.2. The transmission of claim 1 wherein a first of the five torquetransmitting mechanisms is selectively engageable to interconnect thefirst member of the first planetary gear set and the second member ofthe second planetary gear set with the first member of the fourthplanetary gear set.
 3. The transmission of claim 2 wherein a second ofthe five torque transmitting mechanisms is selectively engageable tointerconnect the third member of the first planetary gear set and thefirst member of the second planetary gear set with the first member ofthe fourth planetary gear set.
 4. The transmission of claim 3 wherein athird of the five torque transmitting mechanisms is selectivelyengageable to interconnect the second member of the third planetary gearset with the first member of the fourth planetary gear set.
 5. Thetransmission of claim 4 wherein a fourth of the five torque transmittingmechanisms is selectively engageable to interconnect the second memberof the fourth planetary gear set with the first member of the fourthplanetary gear set.
 6. The transmission of claim 5 wherein a fifth ofthe five torque transmitting mechanisms is selectively engageable tointerconnect the second member of the fourth planetary gear set with thestationary element.
 7. The transmission of claim 1 wherein the firstmembers are sun gears, the second members are carrier members, and thethird members are ring gears.
 8. The transmission of claim 1 wherein theinput member is continuously interconnected with the first member of thefirst planetary gear set and the second member of the second planetarygear set and wherein the output member is continuously interconnectedwith the second member of the third planetary gear set.
 9. Thetransmission of claim 1 wherein the stationary element is a transmissionhousing.
 10. A transmission comprising: an input member; an outputmember; first, second, third and fourth planetary gear sets each havingfirst, second and third members, wherein the input member iscontinuously interconnected with the first member of the first planetarygear set and the second member of the second planetary gear set andwherein the output member is continuously interconnected with the secondmember of the third planetary gear set; a first interconnecting membercontinuously interconnecting the second member of the first planetarygear set with a stationary element; a second interconnecting membercontinuously interconnecting the third member of the first planetarygear set with the first member of the second planetary gear set; a thirdinterconnecting member continuously interconnecting the third member ofthe second planetary gear set with the first member of the thirdplanetary gear set; a fourth interconnecting member continuouslyinterconnecting the third member of the third planetary gear set and thethird member of the fourth planetary gear set; and a first torquetransmitting mechanism selectively engageable to interconnect the firstmember of the first planetary gear set and the second member of thesecond planetary gear set with the first member of the fourth planetarygear set; a second torque transmitting mechanism selectively engageableto interconnect the third member of the first planetary gear set and thefirst member of the second planetary gear set with the first member ofthe fourth planetary gear set; a third torque transmitting mechanismselectively engageable to interconnect the second member of the thirdplanetary gear set and the output member with the first member of thefourth planetary gear set; a fourth torque transmitting mechanismselectively engageable to interconnect the second member of the fourthplanetary gear set with the first member of the fourth planetary gearset; and a fifth torque transmitting mechanism selectively engageable tointerconnect the second member of the fourth planetary gear set with thestationary element, and wherein the torque transmitting mechanisms areselectively engageable in combinations of at least two to establish atleast eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.
 11. The transmission ofclaim 10 wherein the first members are sun gears, the second members arecarrier members, and the third members are ring gears.
 12. Thetransmission of claim 10 wherein the stationary element is atransmission housing.
 13. A transmission comprising: an input member; anoutput member; first, second, third and fourth planetary gear sets eachhaving a sun gear, a carrier member, and a ring gear, wherein the inputmember is continuously interconnected with the sun gear of the firstplanetary gear set and the carrier member of the second planetary gearset and wherein the output member is continuously interconnected withthe carrier member of the third planetary gear set; a firstinterconnecting member continuously interconnecting the carrier memberof the first planetary gear set with a stationary element; a secondinterconnecting member continuously interconnecting the ring gear of thefirst planetary gear set with the sun gear of the second planetary gearset; a third interconnecting member continuously interconnecting thering gear of the second planetary gear set with the sun gear of thethird planetary gear set; a fourth interconnecting member continuouslyinterconnecting the ring gear of the third planetary gear set and thering gear of the fourth planetary gear set; a first torque transmittingmechanism selectively engageable to interconnect the sun gear of thefirst planetary gear set and the carrier member of the second planetarygear set with the sun gear of the fourth planetary gear set; a secondtorque transmitting mechanism selectively engageable to interconnect thering gear of the first planetary gear set and the sun gear of the secondplanetary gear set with the sun gear of the fourth planetary gear set; athird torque transmitting mechanism selectively engageable tointerconnect the carrier member of the third planetary gear set and theoutput member with the sun gear of the fourth planetary gear set; afourth torque transmitting mechanism selectively engageable tointerconnect the carrier member of the fourth planetary gear set withthe sun gear of the fourth planetary gear set; and a fifth torquetransmitting mechanism selectively engageable to interconnect thecarrier member of the fourth planetary gear set with the stationaryelement, and wherein the torque transmitting mechanisms are selectivelyengageable in combinations of at least two to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.
 14. The transmission of claim 13wherein the stationary element is a transmission housing.